public class BinaryTree {
    static class TreeNode{
        public char val;
        public TreeNode left;
        public TreeNode right;
        public TreeNode(char val) {
            this.val = val;
        }
    }
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;
        return A;
    }

    //前序遍历
    public void preOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        System.out.print(root.val + " ");
        preOrder(root.left);
        preOrder(root.right);
    }

    //中序遍历
    public void inOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        inOrder(root.left);
        System.out.print(root.val+ " ");
        inOrder(root.right);
    }

    //后序遍历
    public void postOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        inOrder(root.left);
        inOrder(root.right);
        System.out.print(root.val+ " ");
    }

    // 获取树中节点的个数

   public int size(TreeNode root) {
       if(root == null) {
           return 0;
       }
       size(root.left);
       size(root.right);
       count++;
       return count;
   }

   //子问题思路
    public int size2(TreeNode root) {
       if(root == null) {
           return 0;
       }
       return size2(root.left)+size2(root.right)+1;
    }

    // 获取叶子节点的个数
    int count  = 0;
    public int getLeafNodeCount(TreeNode root){
        if(root == null) {
            return 0;
        }
       if(root.left == null && root.right == null) {
           count++;
       }
       getLeafNodeCount(root.left);
       getLeafNodeCount(root.right);
       return count;
    }

    // 获取叶子节点的个数
    public int getLeafNodeCount2(TreeNode root){
        if(root == null) {
            return 0;
        }
        if(root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) + getLeafNodeCount2(root.right);
    }

    // 获取第K层节点的个数
    int getKLevelNodeCount(TreeNode root,int k){
        if(root == null) {
            return 0;
        }
        if(k == 1) {
            return 1;
        }
        return getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right,k-1);
    }

    // 获取二叉树的高度
    int getHeight(TreeNode root){
        if(root == null) {
            return 0;
        }
        return Math.max(getHeight(root.left),getHeight(root.right))+1;
    }

    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if(root == null) {
            return null;
        }
        if(root.val == val) {
            return  root;
        }
        TreeNode l = find(root.left,val) ;
        if(l!= null) {
            return l;
        }
        TreeNode r =  find(root.right,val);
       if(r != null) {
           return r;
       }
       return null;
    }

}

